Screens widely used in the market are liquid crystal displays (LCD) and organic light emitting diode displays (OLED display, hereinafter referred to as OLED). OLED displays include passive matrix organic light emitting diode (PMOLED) and active matrix organic light emitting diode (AMOLED) displays, wherein AMOLED displays are implemented in the configurations of low temperature polysilicon (LTPS) backplanes+fine metal masks (FMM) and of oxide backplanes+white light organic light emitting diodes+color films.
The fine metal mask method is that OLED material is vapor-deposited on the LTPS backplane according to a predetermined program by a vapor deposition method, and a red, green and blue device is formed by utilizing a pattern on the FMM. The evaporation is carried out in a vacuum chamber, a glass substrate is taken from the upstream by a substrate holding device and sent to each chamber, and then taken out from the chamber and sent to the downstream by the substrate holding device after evaporation. The substrate holding device under the vacuum condition is different from the substrate holding device under the atmospheric condition. The substrate holding device under the atmospheric condition adsorbs the glass substrate to the substrate holding device through vacuum adsorption. However, the substrate holding device under the vacuum condition cannot adopt this method anymore and can only block the glass substrate by stop mechanisms without excessive sliding to fly out and damage the glass substrate. However, the defects of this method are that the substrate holding device can only operate at low speed; meanwhile, the position of the glass substrate sent to the evaporation chamber is different each time because the glass substrate is easy to slide on the substrate holding device under the vacuum condition, so that the alignment time is prolonged; and if the speed of the substrate holding device is increased, the risk that the glass substrate is easy to fly out to cause damage to the glass substrate is greatly increased. At present, it is urgent to shorten the production time and improve the productivity of single product.